发生( )，违约方可援引不可抗力条款要求免责。
Piggybackisasystemofunitizedmultimodallandtransportby（）.
下列()是物权凭证。
FIhascreatedseveraldocumentsandforms，theyare（）.
AccordingtoINCOTERMS2000,whichgroupsofthefollowingtradetermsmeanthatthesellershouldcontractforthecarriageofthegoods.
